Early motorcycle frames were constructed in rigid fashion in a shape which provided an essentially vertical structure in the front and longitudinal frame structure which extended from the upper and lower part of the vertical structure to a point of convergence at the axle of the rear wheel.
The rigid frame provided a rough and unsafe ride and considerable effort has been extended to provide a suspension means for the rear wheel which would increase the comfort and safety of the motorcycle.
Devices prior to applicant's device have consisted primarily of modifying the main frame such that the longitudinal frame structure is terminated in the seat area and instead of continuing on to the rear axle, are connected by a second vertical structure to provide a rigid main frame. Added to the main frame is a fork structure to support the rear wheel. The fork structure is essentially in the shape of a tuning fork with the open end to the rear, supporting the rear axle and wheel. The closed end of the "tuning fork" is pivotally mounted to the second vertical structure. With this configuration various springs and shock absorbers have been inserted between the tuning fork and main frame to provide a spring mounted rear wheel. Disadvantages and limitations inherent in these solutions to the problem included the fact that the frame configuration was altered and the streamlined appearance of the original frame was lost, the integrity of the rear structure was not satisfactory, the present systems tend to be subject to unbalance in their suspension, and the spring or shock absorber means are exposed external to the frame.